starterProjects support

[l0rd]

Description

starterProjects are currently ignored by the DevWorkspace operator as there is no interaction with the developer.

But if a client, like the Che dashboard, allow the developer to chose one starterProject, then the choice should be specified in the DW object so that the DWO can use it as that CR project. For that we can introducing spec.selectedStarterProject:

apiVersion: workspace.devfile.io/v1alpha2
kind: DevWorkspace
spec:
  template:
    attributes:
      controller.devfile.io/use-starter-project: project-1
    starterProjects:
      - name: project-1
        git:
           (...)

Additional context

This work should be part of the epic to support registry.devfile.io: eclipse-che/che#20251